A Low Power Usage Refrigerator For Off-Grid

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In the south refrigeration is probably the most challenging part of living off-grid on a budget.  It is certainly possible to live without it – our ancestors did and we have – but it makes handling our milk and cheese much more productive.  Our solar power system is very small, less than 300 watts, as is our budget so investing in more power and one of the refrigerators designed for off-grid use (the Sunfrosts or propane models) wasn’t an option.  After some research we have found a way to have ample refrigerated space that will operate within the constraints of our small system – the converted chest freezer.

The process is simple.  We purchased an external analog thermostat at a brewing supply store.  Cost was about $75.

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The  freezer cord piggy-backs to the rear of the the thermostat cord. . .

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And the thermostat probe is placed in the freezer.  The freezer door has no trouble sealing around the thin probe wire.  The thermostat is set to the desired temperature and when that temperature is reached it cuts all power to the freezer and restarts it when the threshold is exceeded.  We run ours at 46 degrees.

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We had to purchase a new inverter to run the system due to the startup wattage of the freezer.  Our old inverter was 410 watts with a 750 watt surge which was too small. We continue to use it for our other, very small, power needs.  The new inverter is 1000 watts with a 2000 watt surge and handles the freezer startup load with no problems.  After startup the refrigerator pulls around 160 watts for about 10 minutes each hour in 90+ degree weather.  This “costs” us 600 to 700 watts daily which is within the capacity of our system.

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We use plastic bins to organize our food and place those requiring colder temperatures on the bottom.  In the hottest weather we have found that placing several blankets over the lid helps insulate the unit.

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The setup is much more energy efficient than a regular refrigerator for a couple of reasons.  First, the cold air isn’t dumped out every time the lid is opened.  In addition, a freezer is much better insulated than a refrigerator.  An Energy Star freezer (ours isn’t) would probably run even more efficiently.  We looked specifically for a manual defrost model with no light bulb.  When we set up the project we found that our batteries were failing, which made the compressor run rough.  A new set of batteries solved the problem.  The refrigerator does produce quite a bit of condensation and requires wiping out periodically.  Once a month works for us.

2 thoughts on “A Low Power Usage Refrigerator For Off-Grid

  1. I’m thinking I see cheese rounds in the above photo…do you use this for aging your cheese or just storing after aging? I’ve started on my first adventures of cheese making and while I do have a cellar, I’m trying to make sure I don’t have any loss from my efforts! 🙂 Would love to hear any tips or tricks you have in the cheese making process!

    1. I have to use the fridge for aging in the summer, though it’s actualy a bit cold for that. There’s a lot of humidity with this type of refrigeration setup so I have to be vigilant for mold (unless I want blue cheese which seems to be realy easy for me to produce. LOL) My root cellar is not exactly finished, only a large hole under the floor, and will get up into the 70’s in the hottest days of summer, which here are in the 110’s. Our plan is to build a well-insulated room within the hole and maybe get that temperature down a bit, possibly even low enough for cheese but I’m not sure. I’ll be working on a cheesemaking post because this time of the year I struggle terribly with yeast in my cheese. I’m trying some new things and we’ll see how they work.

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